A device of this type is known from German Open Application 34 17 727, in which mold or the casting form is heated in a furnace and after reaching the operating temperature is fed to the next operating station, the changing station in which the mold is coupled with a receptacle containing a liquid thermoplastic synthetic resin.
The heating of the mold with hot circulating air requires a high energy expense and is time consuming, since apart from the quantities of air required to heat the molding, also associated holding elements must be heated. The heating with circulating air also has the drawback that residue particles from previous operating steps pass from the mold which has been cooled and from which the plastic molded sheet has been separated into the circulating air and can be deposited again on the molding surfaces of the mold.
From French Patent 1 600 351 it is also known, further, to heat a biaxially rotatable closed mold from the exterior by means of an infrared radiator so that the pulverulent plastic found in the molding is distributed uniformly over the inner surface of the mold, is there melted and, upon cooling down of the mold, can be removed as a plastic molded sheet. This type of operation also requires a high cost and is time consuming with respect to the sequence of heating and cooling.